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I've flown a piper cadet arrow. The airplane has an engine of 200 horsepower at 2700 RPM. According to the power setting table in the POH, the maximum power we can set is 75% horsepower. With 100% power, we could fly faster (more fuel would burn though). Why doesn't the manufacturer provide the 100% power setting?

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  • $\begingroup$ If you fly in ground effect the whole way to your destination, you can theoretically cruise at 100% power. $\endgroup$
    – kevin
    May 15, 2016 at 14:04

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There are no 100% power setting tables because it is impossible to cruise at 100% power with a normally aspirated engine.

100% power is rarely available, even at takeoff.

It is only available at sea level when the temperature is 15C and the altimeter setting is 29.92".

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    $\begingroup$ Okay, I've got this figured out. What we do is start a commuter airline running back and forth from a strip at the south end of the Dead Sea to one at the north end. We operate only at night, and we fly at full throttle at sea level. It's about a 30 mile flight. If the temp and altimeter are such that we're not quite getting 100%, we can drop to -400 MSL and still be 1000 AGL (or should we say AWL?). $\endgroup$
    – Terry
    May 15, 2016 at 21:40
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100% power on a typical aircraft engine is only good for short durations like takeoff or emergency maneuvers. Sustained 100% power setting will destroy the engine.

Not to mention flying faster is not always a good thing. It means higher aerodynamic loads on the airplane. Especially when you hit some turbulence.

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  • $\begingroup$ There was a down vote. I canceled it with an up vote for the simple reason that this post answers most directly, in my opinion, the question. It would make no sense to have a 100% cruise entry (forgetting that you can't really get that), when doing so would destroy the engine. $\endgroup$
    – Terry
    May 15, 2016 at 19:07
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    $\begingroup$ @Terry Is that true, though? I don't have a list of engines in operation by model, but the top two manufactured GA aircraft (C-172, PA-28) use a Lycoming O/IO-360, which doesn't have a max continuous power, just a rated horsepower. $\endgroup$
    – NathanG
    May 15, 2016 at 20:10
  • $\begingroup$ Destroying an engine and adding unnecessary wear and tear for a negligible performance benefit aren't the same thing. Also, we need to be careful not to confuse 100% power with 100% throttle which could confuse those who aren't familiar with the differences. $\endgroup$
    – Ryan Mortensen
    May 15, 2016 at 20:24
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    $\begingroup$ @Nathan What I probably should have said (in line with MortensenAviation's comment) is something like running an engine at 100% power continuously will greatly reduce it's life and significantly increase the possibility of an engine failure. That said, I'm not a powerplant engineer, but as a child growing up at airports and then later as a GA pilot then airline pilot, the accepted wisdom was that reciprocating aircraft engines are typically not designed to run at 100% power continuously. The primary problem, as I understand it, is heat. $\endgroup$
    – Terry
    May 15, 2016 at 21:33

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